Building blocks are the most economical product for building walls and are often used for perimeter walls or low cost housing projects. Most popular of the blocks are the 140mm blocks for outer walls/load bearing walls and the 90mm blocks for inner dividing walls. The 190mm and 90mm blocks have the same height and length while only the width varies. The 125mm block is sufficient for external walls, but should be built between columns as they are not load bearing walls.